Warp beam letoff for looms



Filed Aug. 26, 1947 T. MIRUSSELL, JR

WARP BEAM LETOFF FOR LOOMS Jan. 4, 1949.

Attorneys Patented Jan. 4, 1949 WARP BEAM LETOFF FORLOOMS Thomas M. Russell, Jr.,, Middltown, Conn, as-

signor to The Russell Manufacturir'i'g"Company, Middletown, Court, a corporation of""Connecticut Application August-26, 1947, Serial No. 770,707

Claims. 1

The present invention relates in general to looms and more especially to improved let-off mechanism for the warp-beam of a loom.

Heretofore it has been customary for loom operators or weavers to be in constant attendance on .the loom in order to check the tension of the warp strands during the life ofthe beam, the usual method of checking the tension being by plucking the threads to get the feel of the tension. If the warp threads were relatively slack, then the weights on thebrake-arms were moved to the outer ends thereof so as to increase thebraking of. the section-beam, whereas if the tension in the warp had increased then the weights were moved inwardly to release the section-beambrake. The. necessity for. constantly changing. the positions of the weights hasgiven rise to abrupt changes in warp tension and a consequent changein the pick point of the web being woven.

In the manufacture of Woven materials fabricated to close tolerances both as to Width and pick such as ladder-tapes and slide fastener tapes, it is of primary importance that the distance from pick to pick or the distance from ladder to ladder of the tape be exceptionally uniform. Since unequal pick spacing is due primarily to non-uniform warp tension, the problem resolves itself. into one of maintaining the tension in the warp substantially uniform throughout thelife of the warpor beam-section.-

An object of the invention is to provide: a superior warpebeain let-01f which is. of relativelysimple construction, embodies relatively. few moving .parts and is capable of maintaining thetension of the warp substantially. uniform for the life of the warp A further object of the invention is to provide a section-beam let-.off mechanism. with .a warproll which .is. mounted on the brake-arm of the mechanism at a point such that the lift effect on the roll of the warp being pulledoff of the back side of the beam is substantially proportional to the decrease in the radius .at which the yarn. is pulled on the section-beam.

A still further object of the invention is to provide an improved section-beam let-off wherein the lift efiect of the warp on the braking-means of .the beam is so closelycontrolled that thewarp is permitted to unwind substantially continuously without jumping and .under substantially-uniformtension as the goods are woven.

With theabove .and other objects in .view, as willlappear to those skilled in .the'arttfrom. the

present disclosure, this invention includes all'fe'a- 2. tures in the said disclosure which are novel over the prior arti I In the accompanying drawings, in which certain modes of carrying outthe present invention are shown for illustrative purposes:

Fig. .1 is a. broken end elevation partly in section of a section-beam let-off embodying the improved means of this invention for controlling the tension of thewarp;

Fig. 2 is a broken plan view of the sectionbeam let-off on line 1-201 Fig. 1;

Fig. 3 is a broken front elevation of the section-beam let-off of Fig. 1, but on a somewhat reduced scale; and

Fig. 4 is a schematic illustration of the sectionbeam let-off of Fig. 1 showing, by the resolution of force vectors, theideal location of the warproll for effecting optimum control of the tension of the warp threads;

Referring to the drawingswhich show an exemplary embodiment of the invention, the frame of the section-beam is indicated'generally at H and comprises apair of parallel substantiallyvertical uprights l2 secured rigidly in laterallyspaced relationship by suitable tie-beams l3 as characterizes loom structures of this type, each upright I I being provided on its rear face M with an open bearing I5 adapted to rotatably support the respective pivotal-means or trunnions I6 of a section-beam indicated generally at l1,

The latter is a substantially-spool-shaped member comprising an axial cllindrical drum l8 of relatively-small diameter having disk-shaped heads is of relatively-large diameter at opposite ends thereof from which project the respective trunnions l6. Formed integrally or otherwise securedon the 1 outerface of each head I19 and concentric therewith is a brake-disk Zilhaving a peripheral groove to accommodate a brake-band 2|. A pluralityof warp threads w is wound on thedrum l8, a full beam being one wherein the spool of warp threads known generally as a warp or warp-beam is substantially equal in diameter to-the diameter of the heads I 9.

with a. vertical slot 26 as shown in Fig, 2 to receive the oppositeends of its respective brakeband; and transverse.axiallyr-aligned apertures 21 which intersect the median line 28 of the brake-arm forwardly of its pivotal fasteningmembers 22 and 23, the latter being located in vertically-spaced relationship above and below the median line. The two brake-levers are supported on the frame I l by a pivotal-member comprising a rod 29 which extends across the frame beneath the section-beam I1, the rod 29 being supported at its opposite ends in transverse axiallyaligned apertures of a pair of supporting-blocks 30 which are bolted or otherwise fastened to the front faces of the respective uprights I2. As shown most clearly in Fig. 2 each brake-arm is pivotally supported on a corresponding end of the rod 29 in juxtaposition to the inner faces of the respective uprights I2 and the supporting-blocks 30 suitable washers 3| being provided to hold the brake-arms in spaced relation thereto. The ends of the rods 29 project beyond the outer faces of the respective supporting-blocks 30 and are adapted to accommodate suitable retainingmeans 32 for securing the rod against endwise movement in the frame. In accordance with this construction when the brake-arms are swung down in a counterclockwise direction as seen in Fig. 1 the relationship of the fastening-members 22 and 23 of the brake-bands and the pivotal-member 29 of each brake-arm is such that each brake-band will be tightened around the periphery of its respective brake-disk so as to prevent free rotation of the section-beam I1; whereas if the brake-arms are lifted their respective brake-bands are loosened to allow the sectionbeam I! to rotate more freely.

The outer free end of each brake-arm has a series of notches in its upper edge for suspending a weight 33 therefrom at various positions therealong. It will be understood that the preferred average tension at any given set of warp threads may vary from beam to beam depending upon such factors as the type of weave and the size and kind of thread being woven. Hence in order to provide for these contingencies the weights 33 are adapted to be set at various positions along the brake-arms to effect the required average warp tension on the yarn. However, having once made this setting the weight is undisturbed throughout the life of the warp-beam. Projecting forwardly from the supporting-blocks 30 of the frame H is a whip-roll frame indicated generally at 34 arranged to support one or more of spacedparallel whip-rolls 35, the latter extending transversely of the beam I1 and being located in a common substantially-horizontal plane above the median lines 28 of the brake-arms.

Cooperatively associated with the brake-arms is a warp-roll 36 which constitutes means for maintaining the tension in the warp substantially uniform throughout the life of the beam. To this end the warp-roll constitutes a rod 36 which extends transversely across the width of the frame and is secured at its opposite ends respectively to the respective brake-arms by suitable brackets 31 fastened thereto.

Although the theoretically exact position of the warp-roll has been discovered to be'substantially at the point 369, as shown by the vector diagram of Fig. 4 and hereinafter described, for all practical purposes the warp-roll 36 may be located below the median lines 28 of the brake-arms and rearwardly of the pivotal-member 29 thereof. More particularly, assuming for the purposes of illustration only that the distance from the pivotal-member 29 of the brake-arms to the weight 33 at the outer ends thereof is substantially 16 units, then the distance, onthe median lines 8 of the brake-levers, from the pivotal-member 29 to the axis of the warp-roll 36 should be substantially 5 units, the axis of the warp-roll 36 being located also substantially 1 units below the median lines of the brake-levers. The warp threads w of which a plurality are being unwound simultaneously from the beam ii are pulled off of the back side of the beam under the warp-roll 36 and then upwardly and forwardly over the whip-rolls 35 to the loom.

In the operation of the improved section-beam let-ofi as the warp (whether a single thread or a plurality of threads) is pulled off of the back of the beam underneath the warproll 36 and over the whip-rolls 35 the tension in the warp exerts a lifting effect on the warp-roll which increases as the tension in the warp increases and decreases as the tension in the warp decreases. Were it not for the improved tension controlling warp-roll of this invention the tension in the warp would vary over a relatively wide range depending upon the effective radius of the warp-beam. That is to say for a full beam the force movement acting to overcome the retarding force of the brake (assuming the latter to be substantially constant) equals the relatively-large radius of the full beam multiplied by the tension in the warp; whereas for an empty or nearly empty beam the radius of the force moment is relatively small and hence the warp must be put under greater tension in order to overcome the same braking force.

However by providing the warp-roll 36 on the brake-arms in the position shown and described herein any tendency for the tension in the warp to increase as the effective diameter of the beam decreases increases the lift effect on the brakearms thus releasing the brake and relieving the tension in the warp as a consequence of which the warp tension remains substantially uniform or within a very limited range. In fact it has been found that with an average required warp tension of lbs. the warp tension varies only from a maximum limit of lbs. to a minimum limit of 118 lbs. throughout the life of the beam. In this connection reference should be made to Fig. 4 which shows a vector diagram of the forces acting on the warp-roll 36 to lift the brake-arms both when the section-beam is full and when it is substantially empty. Assuming the warp tension is substantially uniform then for a full beam the direction and magnitude of the force vectors acting on the warp-roll 36 to lift the latter are as indicated at Tw the resultant of these forces being R. Similarly for a nearly empty beam the direction and magnitude of the force vectors acting to lift the warp-roll 36 are as indicated at Twl and R1. Resolving the resultants R and R into vectors acting at right angles to a line I through the center'of the warp-roll 360 and the center of the pivotal-member 29 of the brake-arms produces the vectors L and LI which represent the lift effect on the warp-roll. That is to say when a the section-beam is full the lift eifect L on the brake-arms is relatively small and hence the brake holds the beam from rotating freely whereas as the warp-beam becomes smaller in diameter the lift effect Ll increases thereby releasing the brake and permitting the beam to rotate relatively freely so as not to over-tension the warp.

In the vector diagram of Fig. 4 the position of the Warp-roll denotated at 366 is its theoretically correct position and is seen to be above the position it has in the actual application of the invention as shown in Fig. 1. Although the latter position of the warp-roll 36] is highly satisfactory istwithinrthe i rvi we a e"in nt on t loca he w rnw ollm tethe ret c ll q restpos on Moreover it is; reasonedthat the theoretically corre tlp s ti n o the' arnoll ormain substantially uniformtension, in: the warp may be determined matlrlernaticallyrand;to this end a formula has been evolved for expressing the tension in the warpin terms of the length of the brake-arms, the weight, the effective radius of the warp-beam and theilift effect: of the warp on the brake-arms,v ltis belisyedthat the basic formula defining the relationship of these factors is as follows:

where Tw=the tension in the warp in poundsa W=the total weightehungronothe end of the brake-arms.

R.=the effective radius ininches at which the warp is coming off i of tthebeam.

A1==distance in inchesweight is applied from fulcrum of brake-arms.

A2=distance in inches of warp-roll from fulcrum of brake-arms.

E=the efiiciency of the brake which is: inch pounds of resistance around the section-beam divided by inch pounds around the fulcrum of the brake-arms.

L=the lift factor which is the factor that multiplied by the warp tension gives the relief effect in pounds on the brake-arms at the center of the warp-r011.

This basic formula may be rearranged to give 9 a solution for L the lift factor represented graphically in Fig. 4 in which case:

By locating the warp-roll 35 in the position shown in Fig. 1 which for practical considerations varies somewhat from its theoretically correct position 360 the tension in the warp is held substantially uniform or within an extremely-small range throughout the life of the beam as a consequence of which the width of the fabric and the distance from pick to pick are maintained accurately uniform for producing woven fabrics such as slide-fastener tapes to close tolerances and for effectively eliminating the problem of ladder variation in ladder-tapes. A further advantage resulting from the maintenance of substantially uniform warp tension is the unusually smooth and even delivery of the warp yarn to the weaving point. Heretofore in most left-offs, the tension of the warp yarn builds up to a peakpoint and then drops off thereby causing anintermittent braking action of the section-beam, that is to say, the latter does not unwind uniformly but unwinds in a series of short successive jerks. As a result, the warp threads have been successively pulled taut and then released, thereby creating constant variations in the width of the web being woven. By maintaining the warp tension uniform in accordance with the improved device of this invention, the braking action of the section-beam is leveled off so that the beam moves substantially continuously from pick to pick thereby providing a smooth uninterrupted flow of yarn to the web for insuring the weaving of a fabric of constant width.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the-invention, and v the present em:- bodiments are, therefore, tobe considered in all respects as illustrativeand'not restrictive, and all changes coming within the meaning and equivaleney range of the appended claims are intended to ,be embraced therein.

I claim:

1; In a self-regulating section-beam let-off for looms; a frame; a section-beam; pivotal-means arranged-to rotatably mount said section-beam on said frame; brake-means for saidsectionbeamqcomprising a brake-band, a brake-arm, a pivotal-member arranged to secure the forward end'of said brake-arm to said frame forwardly of the, pivotal-means of said section-beam, and fastening-means arranged to secure the ends of said brake-band to said brake-arm at verticallyspaced points thereof rearwardly of said pivotalmember; a warproller mounted on said brakearm ata point thereon such that the warp of said beam passing from the back side thereof under said roller forwardly to said loom lifts said brake-arm so as to reduce the braking effect of said brake-band in proportion to the'decrease in effective radius of said warp-beam; and a warptensioning weight supported at the rear end of said brake-arm.

2. In a self-regulating section-beam let-off for looms: a frame; a section-beam; pivotal-means arranged to rotatably mount said section-beam on said frame; brake-means for said sectionbeam comprising a brake-band, a brake-arm and a pivotal-member arranged to secure the forward end of said brake-arm to said frame forwardly of the pivotal-means of said section-beam; a warproller mounted on said brake-arm rearwardly of the said pivotal-means of said section-beam the warp of said beam passing from the back side thereof under said roller forwardly to said loom; fastening-members arranged to secure the ends of said brake-band to said brake-arm at vertically-spaced points thereof intermediate said pivotal-member and said warp-roller; and a warp-tensioning weight supported at the rear end of said brake-arm.

3. In a self-regulating section-beam let-off for looms: a frame; a section-beam; pivotal-means arranged to rotatably mount said section-beam on said frame; brake-means for said sectionbeam comprising a pair of brake-bands, a pair of brake-arms and a pivotal-member arran ed to secure the forward ends of said brake-arms to said frame forwardly of the pivotal-means of said section-beam; a warp-roller; means to secure said warp-roller to said pair of brake-arms rearwardly of the said pivotal-means of said sectionbeam and below the median lines of said brakearms the warp of said beam passing from the back side thereof under said roller forwardly to said loom; fastening-members arranged to secure the ends of said brake-bands to the respective brakearms at vertically-spaced points thereof intermediate said pivotal-member and said warproller; and a warp-tensioning weight supported at the rear end of each of said brake-arms.

4. In a self-regulating section-beam let-off for looms: a frame; a section-beam; pivotal-means arranged to rotatably mount said section-beam on said frame; brake-means for said sectionbeam comprising a pair of brake-bands. a pair of brake-arms, a pivotal-member arranged to secure the forward ends of said brake-arms to said frame forwardly of the pivotal-means of said section-beam, and fastening-members arranged to secure the ends of said brake-bands to said brake-arms at vertically-spaced points above and below respectively the median lines thereof and rearwardly of said pivotal-member; a warproller; means to secure said warp-roller to said brake-arms rearwardly of the said brake-band fastening-members and below the median lines of said brake-arms the Warp of said beam passing from the back side thereof under said roller forwarclly to said loom; and a warp-tensiomng weight supported at the rear end of each of said brake-arms.

5. In a sell-regulating section-beam let--ofi for looms: a frame; a section-beam; pivotal-means arranged to rotatably mount said section-beam on said frame; brake-means for said sectionbeam comprising a pair of brake-bands, a pair of brake-arms, a pivotal-member arranged to secure the forward ends of said brake-arms to said frame forwardly of the pivotal-means of said section-beam, and fastening-members ar ranged to secure the ends of said brake-bands to said brake-arms at points above and below respectively the median lines thereof and rearwardly of said pivotal-member; a warp-roller;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 452,021 Schaum May 21, 1891 1,593,214 Holmes July 20, 1926 1,628,540 Hughes May 10, 1947 FOREIGN PATENTS Number Country Date 18,544 Great Britain Aug. 18, 1906 32,951 Germany Mar. 18, 1885 

